As many as one in 100 children may be intolerant to gluten which is found in cereal flour, according to recent research. Symptoms can include tiredness, anaemia, weight loss, diarrhoea and constipation.
BBC News Online's Fiona Murray talked to one man who lives with the disease.

If Stephen McCavery accidentally eats the wrong food, he will fall ill within hours.

Stephen McCavery: Lives with coeliac disease

He will suffer severe stomach cramps, bloating, and if a large amount is consumed would become extremely lethargic.

The 41-year-old has coeliac disease, an intolerance to gluten, effecting about one in 120 people in Northern Ireland.

Had he not been diagnosed, Stephen says he could have ended up with colon cancer.

"It's a shock to the system to be told you have the disease. It's really scary and difficult at the start, but once you get to grips with it, it's quite easy," he said.

At his County Down home, he uses one side of the toaster, his wife uses the other. He has a separate chopping board and butter dish.

These stringent measures help prevent him being contaminated by any traces of gluten.

Stephen's condition was diagnosed by accident, after going to the doctor with a persistent cough.

"I had the cough for about two months when I went to the doctor. He took some blood tests.

"They found that the red cells in my blood were deformed - and it was nothing to do with the cough.

"They then looked at the building blocks of the red blood cells and they found I had no vitamin B12 in my body. B12 is absorbed in the upper part of the gut.

"There was something wrong as it wasn't getting absorbed, and I had been eating the things I should have been eating."

A biopsy later diagnosed the disease, explaining Stephen's ability to eat whatever he liked without putting on weight.

The condition is caused by oversensitivity to gluten of the lining of the small intestine.

This leads to inflammation of the gut, and an inability to absorb adequate nutrition from food. Gluten is found in wheat, barley, oats and rye.

Stephen said he had symptoms of the disease, such as abdominal upsets, without realising.

Gluten is found in wheat

Diagnosis of the disease has changed his life, but despite working in the food industry, it was a steep learning curve for Stephen to find out what he could eat.

"I virtually had to cut out everything overnight because I just didn't know what I could eat," he said.

"For the first three months, I lived on fresh meat and fresh vegetables - stuff that I was 100% convinced wasn't contaminated."

Now Stephen adheres to a strict gluten-free diet.

"You can get bread and spaghetti on prescription. I also eat meat and poultry, fish and vegetables in their natural state," he said.

"Five years down the line, I have a fairly good knowledge of what I can and cannot eat now. So, if I want a packet of crisps, I know if I can eat it.

"You learn through experience. It's restrictive but you get used to it."

However, it is the hidden gluten in many foods which pose a major risk to sufferers. Food labelling is a particular bone of contention.

"Gluten can be in foods, and you don't know it's there," he said.

"For example, you can have flour in ground black pepper; it doesn't have to be labelled as an ingredient because it's considered a packing agent.

"Flour is also added to grated cheese to make sure it doesn't stick together, but it won't be on the ingredients list.

"Anything that's 25% or less of an ingredient doesn't have to be labelled as a separate ingredient."

Going out for a meal can pose problems for Stephen, who believes chefs need to be better educated about the disease.

I don't know how much damage did I do to myself before I was diagnosed, or if it will come back to haunt me

Stephen McCavery

When he attends a business lunch he phones ahead to ensure he is catered for. Often, he does without food until he gets home.

But he was horrified at a recent discovery.

"In the last month, I learned that restaurants have a habit of dipping steak in flour to seal it. That has scared the life out of me."

The charity, Coeliac UK, offers support to sufferers.

Liz McCorkell, the organisation's regional manager for Northern Ireland and Scotland, said diagnosis of the disease had improved.

"The trouble is that it can manifest itself in a number of ways, its symptoms are similar to other illnesses," she said.

"My doctor had just come back from a lecture on coeliac disease, when I went to him.

"I had been treated for six years for irritable bowel disease."

Coeliac UK produces a booklet of suitable foods and many supermarkets are now offering a good range of gluten-free food. But they are expensive - a loaf of bread can cost about £4.

Researchers believe that coeliac disease is often triggered in childhood, but symptoms might not appear until years later.

With this in mind, Stephen pays particular attention to the diet of his daughter, Laura, who is nearly four.

"We are very careful about Laura," he said, "especially in light of the research about children.

"Because I don't know how much damage did I do to myself before I was diagnosed, or if it will come back to haunt me."